The present invention is generally concerned with composite can construction, and more particularly with a composite can uniquely provided with a hermetically sealable liner for adaptation of the composite can to vacuum packaging. In conjunction therewith, the present invention is also specifically concerned with a unique method of providing the basic composite tubular body with a liner secured solely at the opposed ends thereof for a free inward collapsing, upon being subjected to a reduced internal pressure, independently of the tubular body and without the introduction of adverse forces to the tubular body.
It is now recognized that substantial economies, as well as environmental advantages, can be affected by the use of inexpensive composite containers, as opposed to the traditional glass and metal containers. However, and primarily because of the lack of inherent strength in composite containers, substantial difficulties arise with regard to the packaging of particular products, as well as the use of particular packaging procedures.
This is particularly the case wherein a pressure differential is to be developed between the interior of the container and the ambient atmosphere. More specifically, attempts to vacuum package products within composite containers have, to a large degree, been commercially unsuccessful in that the developed pressure differential causes either an actual or a substantial likelihood of an inward collapsing of the tubular wall. This in turn results, at the least, in an unattractive and potentially unmarketable package, and, in the extreme, in a package whose contents have been exposed and contaminated.
Various and substantial efforts have been put forth with a view toward increasing the potential of composite containers as a universal packaging means. The following U.S. patents constitute the most pertinent known prior art relating to the provision of impermeable or hermetically sealable liners, the particular area of concern with regard to the invention herein.
2,328,798: Gardner PA1 3,383,026: McGee PA1 3,462,063: McGee PA1 3,487,989: Rausing et al PA1 3,662,944: Joosten, Sr. PA1 3,666,163: Ignell PA1 3,799,423: Cvacho PA1 3,978,232: Dodsworth et al PA1 4,010,230: Repenning PA1 2,301,092: Thompson et al PA1 3,150,575: Couzens et al PA1 3,253,520: Cvacho PA1 3,376,180: Larson et al
In each instance, it will be appreciated that the liner is individually formed and mounted within the formed outer tube or the like.
The following U.S. patents are noted as examples of known tube winding procedures and apparatus.
The patent to Larson et al is of particular interest in that it does illustrate the spiral winding of a container about a separately formed liner. However, the liner in Larson et al is extruded, requiring substantial and elaborate equipment above and beyond that normally associated with the more conventional spiral winding apparatus. Further, the liner in Larson et al is secured to the formed tube throughout the complete extent thereof, providing in effect a completely laminated inner ply.